RST Spare TyreReplacement tyres The Radar replacement tyre is intended to help drivers to temporarily regain their mobility in the event of a tyre breakdown. This space-saving tire is designed for temporary use only and can help you get off the highway quickly in an emergency and reach the nearest tyre shop. The replacement tyre is a small, narrow lightweight, which should be driven with a maximum speed of 80 km/h and a tyre pressure of approx. 4.14 bar.